Ground working tools such as plows, discs, rakes, plows and the like, used with agricultural vehicles such as tractors, skid loaders, combines, and the like, are ubiquitous in the agricultural industry. As an agricultural vehicle towing a ground working tool travels across a field, agricultural processes such as digging, scraping, plowing, plating, and/or fertilizing are performed. However, such tools are vulnerable to damage resulting from collisions with debris such as rocks, trees, and the like. Manufacturers of such tools have worked for years to produce ground working tools that are responsive and easily retractable so that the tools do not suffer damage when obstructions are encountered during such activities.
Ground working tools described above typically include some sort of trip mechanism designed to allow the tool to change from an operating, “untripped” position to a non-operating, “tripped” position in the face of a collision with an obstacle. These trip mechanisms typically include coiled springs configured to allow the tool to yield when obstacles are encountered. However, springs that are fully exposed to the elements may cause the springs to stick due to accumulation of dirt and debris in and around the springs. Further, exposure to the elements can cause the springs to rust and/or corrode due to continued exposure to harsh conditions.
Additionally, these spring-based systems typically have a fixed or very difficult to adjust “trip-out” force. That is, the amount of force required to cause the system to trip is difficult or impossible to adjust. This is a significant limitation of such systems since field conditions can vary significantly from field to field or season to season.
Accordingly, some systems combine hydraulic cylinders with springs for automatically tripping the tool away from the obstruction while providing a variable trip-out force by adjusting the pressure in the hydraulic cylinder. However, this type of mechanism can result in overpressure conditions, requiring the operator to manually recharge the hydraulic cylinder to its predetermined pressure setting, which can be a time-consuming procedure.
Additionally, hydraulic cylinders are significantly more costly to manufacture, maintain, and replace than springs. For example, for proper operation, it is important to maintain clean, smooth surfaces along the sliding surfaces of the cylinders and protect against damage to the chrome, nitride coated surfaces, seals, and the like. The costs associated with such maintenance is compounded by the fact that as many as 80 or 90 individual cylinders may be incorporated into a given system.
In an effort to control costs, the cylinder for hydraulic trip systems are typically “single acting” cylinders with no over extending limitations. The trip system is designed to have a limiting geometry so the cylinder maintains an appropriate working geometry. However, this design exposes the rod end of the cylinder when in the untripped position because in this working position the cylinder must be extended. Furthermore, this design forces the cylinder to be in a vertical orientation in an attempt to prevent dust and dirt build up on the cylinder. Accordingly, the design requires an adjustment system for the shank to be built into the trip. Because of these design restrictions, the trip system becomes cumbersome in size and more costly to build. A large tip size is a significant drawback when mounting 80, 90, or more trips systems on an air drill frame.
As a result, a need exists for a trip mechanism for a ground working tool which effectively protects the tool from obstructions while simultaneously allowing quick and easy adjustment of trip mechanism.